feat(ui): add roadblock reply field to the ROADBLOCK card

A task that reports a roadblock but finishes successfully (Done/WaitingForReview/
Failed/Cancelled) had no way to answer it short of a full reset-and-rerun, losing
the run's context. Adds a reply textbox + Send button to the existing ROADBLOCK
card, modeled on the AskUser question card, that resumes the session via
ContinueTaskAsync with the user's own text. Gated on LatestRunSessionId (disabled
with a hint when there's nothing to resume); failures surface through the footer
error strip instead of a modal.

src/ClaudeDo.Ui/ViewModels/IslandsShellViewModel.cs

@@ -256,6 +256,7 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
             if (Lists.SelectedList is { } row)
                 Lists.LetClaudeHandleListCommand.Execute(row);
         };
+        Details.ErrorReported += FlashFooterError;
         Details.CloseDetail = () => Tasks.SelectedTask = null;
         Details.DeleteFromList = row =>
         {